How cold is that rain?

How cold is that rain?

 

If you’ve stood outside in the rain, even on a warm day, you’ve felt the chill of the rain. There are two reasons, the first being that water takes up heat from your skin much faster than does air when both the rain and the air are at the same temperature that’s lower than body temperature – the same reason that metal feels cold even when it’s at room temperature or even above.  The second reason is that the rain is at a lower temperature than the air, and we can estimate just how much cooler it is, based on air temperature and relative humidity.  We can also reverse the calculation, to estimate relative humidity from the temperatures of the air and of the rain (catch the rain in an insulated cup).

I present the theory and examples in a PDF document (I wrote it in Word with MathType – too many equations to save and paste into WordPress handily!).  I hope you enjoy it.

You can skip to using the theory to estimate the rain’s temperature from the air temperature, relative humidity, and air pressure.  I created a spreadsheet, in which you can enter the values in either metric or English units.  There is a second section to it, in which you can do the inverse, calculating the relative humidity from the air temperature, rain temperature, and air pressure.

The image attached is, of course, not freely falling rain but rainwater draining from a roof canale on our Southwest style flat roof.  It was intriguing to see how the flow breaks up and shortly generates slightly flattened spheres.

Making spider silk for fun and profit: worth it?

Company using microbes to make spider silk garners $123,000,000 in venture capital.

This is a story reported on the Tech Crunch site, about Bolt Threads.  The proposed uses seem to center on wearable textiles (vs. engineering textiles).  Why spider silk?  It’s touted to be stronger than other polymers – stronger than Teflon, in the Tech Crunch page. That’s a mistake, since they meant Kevlar, the amazing polymer used in bulletproof vests.  Spider silk is also claimed to be stronger than steel.  Consider these points:

  • “Strength” is one of many properties of a structural material (yes, textiles are structures of a special sort); stiffness and toughness are equally important.
  • These properties commonly trade off against each other, and in any application of a material – polymer, steel, carbon fiber, etc. – there are choices to make. Brick is a strong material but it’s very un-tough, as are ceramics in general.  Steels are strong but the strongest steels aren’t the toughest (meaning taking the most energy to break).  I have a quick summary of properties below.
  • Many structural materials have properties that vary with the environment. The steel in WW II Liberty ships became brittle at cold North Atlantic Ocean conditions, and they sometimes broke apart under wave stresses.
  • Spider silk is notorious for its properties depending strongly on humidity and temperature.

Another property of note is resilience.  When stressed (stretched along its length, for example, some spider silk stays stretched.  Not so good for a tie.  Of course, silkworm silk is good here (doesn’t stretch, is stiff), and some types of spider silk are resilient, and stiff, like silkworm silk.  Pick the right type of spider silk, and perhaps blend several types.

  • As many investigators have noted, spider silks vary; some classifications put as many as 27 types in play. Bolt Thread likely will need to make a number of different silks.  Look at orb-weaving spiders, the common web-makers.  They use strong and resilient silk for the main radial lines and nonresilient, sticky silk for the cross lines.  The strong lines keep the web intact, but they would just kick an insect back out rather than trap it.  The sticky lines do the trapping.
    • One use I saw touted the use of spider silk instead of steel cables on aircraft carriers for arresting the landing of an aircraft. Two scenarios seem to have be implied.
      • One is that the trapping type of silk, or flagelliform silk, be used, as if catching a very big fly. As Stephen Vogel notes in his oh-so-readable book, Cats’ Paws and Catapults, spider silk is nonresilient; the energy it would absorb would go into making so much heat that the net would melt. So, that won’t work.
      • The other is using spider silk as the arresting cables, the ones that the aircraft’s tailhook engages, or perhaps the balancing cables that take the shock of stopping a landing aircraft by paying out from a drum with hydraulic damping, like big car shock absorbers. There, the tough and strong silk might be used.  A variant arresting method, for aircraft missing a tailhook, is to put out a big net instead of the arresting cable.  OK, but why go to spider silk, which is likely harder to maintain and in a function where weight is not critical?
    • Spider silk really isn’t stronger than Kevlar. Both (some) spider silk (drag lines) and Kevlar are stronger than steel, and notably better than stell per unit weight, but Kevlar is stronger than spider silk by a factor of 1.5 to 7.  Nothing is better for strength.

    Here’s a rundown of strength, stiffness, toughness, resilience, ductility, and some shape dependence of material failure.   We can conclude at the end that spider silk has a mix of properties that suit it to certain uses, choosing it over Kevlar (or steel, or putty, or ….), but not to other uses.  Using it for high-priced silk ties is an affectation for the rich.  I’ll wait to hear what real uses are in line.

We can look at a graph of the extent to which a material deforms (its fractional change in length) against the stress put on it (the force over an area).  Such a plot is useful for materials that have the same properties in any direction, or isotropic materials, though one can use it for materials whose properties vary by direction, if one specifies the direction.  (There are also differences in stresses applied in one direction, as extension or compression, and shear stresses applied nonuniformly, as in trying to stretch a material into a distorted rectangle or parallelogram.)

Here’s a simple comparison of two materials, well, OK, three.  Material A deforms a lot less than does material B, under the same stress.  Or, you can say that material A takes a lot more stress to deform it by a given amount.  It has greater stiffness.  We can take the slope of stress vs. strain at any point and call it stiffness.  For many materials, stiffness is pretty constant over a range of stress levels – e.g., steel.

 

Strength is the amount of stress needed to make the material break apart.  Material A isn’t as good as B.

 

Toughness is the total energy needed to make a material fail.  It’s the area under the curve from zero stress to failure.  Again, B is better.

 

Resilience is the ability to return to the original shape when stress is relieved.  We tend to like that.  Spring steel needs to be resilient.  Putty is non-resilient, and we like that for keeping it in place once we apply it.  I drew a line on the side of a related but distinct material, A2, indicating what strain remains when the stress goes down.  It ends with a non-zero strain when stress is completely removed.

Material A2 is not fully resilient; it might be resilient, however, from its new, once-stretched state, under later stresses.  If so, we can call the material ductile, able to be deformed and take on a new, resilient state.  It’s what we do in forming metals with dies by stamping, pulling through wire dies, forging, etc.

We can also call resilience elasticity.  The opposite of it is plasticity – undergoing plastic deformation.

 

 

I’ve attached another graph with an explicit comparison of spider silk to Kevlar

OK, spider silk is tougher than Kevlar if not stronger and not stiffer (of course, we knew it wasn’t stiffer!).   Its resilience depends on how far you stretch it – probably not as resilient as Kevlar, but close.

 

Model rocketry – equations and tests

Sort of a one-stop-shop for model rocketry theory, experiments, and data analysis for a high-school class, or an advanced middle-school class such as we have at the Las Cruces Academy:

Tsiolkovsky derived the equation for the final speed of a rocket in free space (no air drag) in 1903!  I have a derivation here, plus an elaboration that goes on to consider air drag and gravity for a surface launch, and another one that looks at how a rocket has to be designed with propellant, payload, and basic infrastructure (the shell, we may say).

Our students at the Las Cruces Academy did rocket launches in the desert, measuring the altitude achieved with geometric measurements.

Some pictures are useful.  Check out the link on the LCA News and Events page.

The results for altitude vs. rocket motor impulse are summarized in a spreadsheet.  Altitude looks to be linear in impulse, in line with numerical simulations I performed.  We had to be very careful with our measurements, btw, since small errors lead to big errors in altitude.

A sideline: where does the kinetic energy go, partitioned between exhaust gases and the rocket?  At burnout for a serious rocket, there’s more in the gases than in the payload that’s left.

Adventures in light propagation – teaching and research

This multilayered post can be followed from one PDF document, or by the explicit links given below in the description of the whole study.  The post covers:

  • Teaching:
    • Working with students to make a light intensity detector using a photodiode.  It measures photon flux density in the visible portion of the electromagnetic spectrum.
    • We went on to use it as the detector in a (spectro)photometer for measuring the concentration of methylene blue dye illuminated with light from a high-intensity yellow LED.
  • Research:
    • The main point I just completed writing up is the use of radiative transport equations that I developed for estimating scattered light within a uniform canopy of plants.    The solutions for the fluxes of a direct beam and diffuse light together are analytic, in term of algebraic and exponential quantities.
    • The model also is useful for simulating the propagation of light inside leaves for modeling photosynthetic rates of leaves with different structures and pigmentations.  I have a number of publications on this (which I can link later, when I find PDFs of them.  One interesting prediction I made is that leaves with half-normal chlorophyll content should allow sharing of light with leaves deeper in a dense canopy, ultimately giving an 8% increase in biomass and yield.  John Hesketh’s group at the University of Illinois tested this in the field and got an 8% increase over fully green leaves! (Pettigrew WT, Hesketh JD, Peters DB, et al. (1989) Characterization of canopy photosynthesis of chlorophyll-deficient soybean isolines. Crop Science 29:1025-1029).
    • Recently (Nov.-Dec 2017) I extended it to multiple layers of different optical properties.  The challenge was testing it rigorously and making a comprehensive explanation with text and equations.

Back toward teaching: I wanted to verify that the photodiode circuit responded linearly to flux density.  I made a simple error in using layer scattering media too close to the detector, invalidating Beers’ law for the direct beam alone.  However, I then dove into the propagation of direct and diffuse light for its inherent interest.

The lead PDF document here has several sections:

  • The most recent inquiry: is the photodiode responding linearly to photon flux density?
  • The radiative transport equations
  • A few notes about extensions to nonuniform canopies

Within the lead document are links to several others.  The links are imbedded within the lead document; the links are also noted directly here:

  • A short write-up of the electronic circuit for the photodiode detector
  • Fixing-approximations.pdf:” A set of notes on improving a whole-canopy flux model (light, CO2 uptake and respiration, transpiration) in the representation of:
    • The enzymatic model of photosynthetic carbon fixation, bridging the cases of high light and low light
    • The equations for radiative transport, with their full derivation and some numerical results
    • A discussion of extensions of the model for leaves varying in absorptivity with depth in the canopy, or that are clumped, or that vary in temperature as they transpire water at different rates
    • In turn, this PDF references a short Fortran 90 program I wrote to solve the radiative transport equations
    • Also, a link to a 2013 publication I had with Zhuping Sheng, modeling all the fluxes of a pecan orchard.  The relevance is that I cited in this second PDF the modeling of light in a regular array of tilted, ellipsoidal canopies of individual trees.  Sheng did the experimental measurement of fluxes with eddy covariance equipment. I modeled the results, with one surprising finding that pecan trees, unlike every other plant I’ve studied, do not reduce its stomatal conductance and thus its transpiration in very dry conditions.  They operate at high transpiration rates and poor water-use efficiency in these conditions.
    • A couple of references to publications:
      • A model of radiative transport in layered plant canopies represented by finite layers (a finite-element model), as an integral equation that’s readily solved numerically.   I cite this publication because within it I discuss the changing angular distribution of diffuse light with depth.
      • The clever method of colleague and friend Michael Chelle and his former advisor Bruno Andrieu for radiative transport in an arbitrary assemblage of light-scatters.  The method is called nested radiosity, accounting essentially exactly for nearby scatterers affecting light at a given leaf and then via a nice smoothing approximation (mean field) for more distant scatterers.

 

You make more heat than the Sun

Say what?  The sun’s temperature is surely very much higher than our temperature – in fact, in absolute units, it is nearly 20 times hotter (nearly 5800 Kelvin, in scientific units, while we’re less than 310 Kelvin, or K).  The sun is also considerably bigger than any one of us, or all of us. Its mass is about 330,000 times the mass of our own earth, and the earth’s mass is about 86 sextillion times (86 x 1021) more than our tiny little 70 kg or 154 pounds apiece.  Yet the statement in the title is true in one important sense: the average kilogram of our body generates more metabolic heat than the average kilogram of the sun.

 

One way to get at this figure is that, at rest, we put out about 70 Watts, less than the (fortunately less and less common) 100 W incandescent light bulb.  Still, we’re at 1 watt (W) per kilogram.  We eat to maintain that rate.  Over an hour, that 70 W amounts to an energy use of 70 x 3600 Joules.  Now, a Joule is 0.242 calories and a food calorie (Cal) is 1000 of the standard calories, so in that hour we metabolize about  65 Cal. Over a 24-hour day, we then need 24 x 65 = 1560 Cal…well, more like 2,000 if we’re minimally active or 10,000 if we’re top-notch mountain climbers or skiing across Antarctica.

 

How much power, which is energy per unit time, does the sun put out?  By the time sunlight reaches the surface of the earth, its peak at noon is as high as 1000 Watts on a square meter; that’s a hair-dryer’s worth, for every square meter (a bit bigger than a square yard).  Above our atmosphere, it’s higher, about 1360 W per square meter.  It gets more intense as we get closer to the sun.   You can search a book or the Internet for the inverse-square law to find out how much more intense.  Using the fact that we are, on average, 150 million km (93 million miles) from the sun and the sun’s diameter is close to 1,390,000 km (870,000 miles), we can calculate the intensity at its “surface” (remember, no hard surface – it’s a gas bag).  It’s 46,000 times greater than at our distance, or about 63 million watts per square meter, compared to our 70 Watts per 2 square meters of skin surface.  Let’s go on.  Over its whole surface, the sun radiates energy to space.  That surface area is 4 π times the sun’s radius squared, or 6.07 quintillion square meters (6.07 x 1018).  This is 2.36 trillion square miles, if you’d like old English units, and that’s close to a million times the area of the US.  Multiply this by the output per square meter, to get 382 septillion W (3.82 x 1026).  Divide that by the mass of the sun, which is nearly 2,000,000,000,000,000,000,000,000,000,000 kg (or 2 x 1030 in easier notation).  The sun puts out a measly 0.00019 Watts per kg.  You expend 5,000 times more, on a mass or “weight” basis.

 

This low output from the sun is a good thing, so that the sun does not run out of its nuclear fuel in less than its long life of about 10 billion years.  Other stars are much brighter and burn up much faster, in as little as a few million years.  Compared to the sun, we are profligate in using energy…which we capture from the sun through our crops and pastures.  The plants on earth use only 0.3% of the solar energy reaching us, and we capture as food only several percent of what they capture.  This low capture rate can only be helped a little, and it’s why there can’t be too many more of us.

Radio show, Science: let’s take a look

Science: let’s take a look, on radio KTAL LP FM, Las Cruces, New Mexico:

I host an hour-long show each Tuesday at 12-1 PM, Mountain Time.  Find it at 101.5 on the FM dial if you’re in Las Cruces, or stream it live on lccommunityradio.org or radioquetal.org.

I cover a great variety of topics in all the shows,, extending from many branches of science to engineering to math to implications for society.  Guests appear about every other show.

I record each show, edit the audio into distinct segments (cutting it at station breaks), add some imagery, and created videos for YouTube.

Here are links:

Coming up:

  • Have you thanked a bacterium today?
  • Proxima Centauri b: not really habitable; how ’bout keeping Earth habitable?
  • Carbon nanontubes: useful; don’t inhale!
  • How far is it worth driving for cheaper gas? Some algebra
  • Many more guests from near and, I hope, far (scientific colleagues calling in)

Smart Water?

Posted 11 December 2017.

Smart water: ads

As our son, David reported reading: “If you’re paying $4 a bottle for smart water, it’s not working!”

Start with the cost.  Tap water averages about $2 per 1,000 gallons, which is enough to fill

Can it be any better than tap water?   A tiny bit, perhaps.   Regular tap water in almost all US water supplies is actually cleaner than most bottled water, according to independent labs.  Save money, save the landfill waste, save the petroleum used to make the plastic bottles!

(Eau du robinet!)

What could be improved in Smart Water, and how?

Distillation – removes dissolved solids…and SOME of the volatile organic compounds, SOME

Adding in minerals, selectively – why not drink the natural minerals in your tap water?

The makers avoid sodium – fine, in our salt-laden cuisine…but we get so little sodium from our water!

No fluoride – but you  need small amounts of fluoride (GO ON about fluorosis worry)

No heavy metals, arsenic, etc. – well, they’re in your food, unavoidably.  We have lived with U, Hg, etc. our whole 2 Mya as a species

No gluten – ridiculous!  Gluten only comes from wheat and barley, and I haven’t notice public works people tossing either into our water supplies!

What about water purity, in history?

Not a good record, until sanitation started big time in the mid-1800s

Reason to drink wine, beer (maybe! adulterated), strong spirits – why the temperance movement had a basis (along with the transport problem for grain from the US Midwest, e.g.)

Cholera spreads by contaminated water – English well XXXXX

In fact, broadening to sanitation, in general – it was the first major advance in human health!

For our water and food, and then in medicine – the sad story of Joseph Lister XXXX

GO out and thank an LC utility worker, a garbageman!

On, but if you’re a vegan, thank a little dirt in your food, for vitamin B12 …..

Star Talk, with Neil deGrasse Tyson

Neil deGrasse Tyson is one of my favorite persons.  I imagine myself at times traveling with him, John Oliver, and Bill Bryson.  Still, we all put out some stuff that needs comments or corrections.  I just went through Star Talk with Neil deGrasse Tyson, Abridged Edition (National Geographic, 2016).  He had co-authors and editors, so I don’t know who wrote or edited individual items, but here are my notes:

p. 56, about life possibly originating on Mars and being transported to Earth on tektites blasted off the Martian surface by an impactor. Others have proposed this, too. Several ideas militate against this.  First, as Neil (may I use his first name?) admits, live organisms surviving the intense heat and shock of both exiting Mars and landing on Earth is extremely problematic.  Second, the idea that Mars was warm and wet before Earth has less and less support.  The evidence for water on Mars is, well, evaporating in favor of sand having sculpted features.  Third, the whole idea violates Occam’s Razor, which is that the simplest explanation is favored over all complex ones, in the absence of strong evidence to the contrary.

p. 57, that life needs a steady heat source, water, and a critical set of chemicals. This is wholly inadequate. I outline what keeps Earth friendly to life in another essay.  The most egregious error here is the claim that life can use heat, not just to keep water liquid, but as an energy source.  No!  Organisms have to perform biochemical reactions of high energy, several electron-volts’ worth in common terminology (e.g., 1.8 eV for photosynthesis).  Thermal sources in the physiological temperature range are far, far too low in energy, only several percent as large.  The “tail” of the energy distribution, in the eV range, is vanishingly small for thermal sources.  Some physical chemistry or chemical physics needs to be accounted here.

p. 96, about heavy water (D2O) not being toxic, only slowing a host of biochemical reactions. Sure, the isotope effect on chemical reactions is well understood (the zero-point energy of chemical bonds with heavier atoms is lower, making more energy needed to break bonds for chemical reactions), and the effect on rates is rather modest, in most cases. However, animals from flatworms to mammals die when a large fraction of their ordinary protium (hydrogen) is replaced by deuterium.  In mammals, bone marrow and intestinal functions are changed, lethally.  Humans have only been exposed to minor amounts of D2O and then survived.

p. 97, a positive note from me: the profligacy of making and disposing of plastic bottles, especially for water. I may add that tap water is purer than many bottled waters, as analyses have shown! Bottled water is, by and large, a tax on ignorance.  I did verify the calculations about barrels of oil used and number of cars that could be fueled.

p. 99, on water consumed for electric power generation: The only water mentioned her is the steam in the turbines….but water in the turbines is consumed very infrequently; mostly, it’s recirculated, unlike that in old steam locomotives. The major use of water in electric power generation in thermal power plants (still our biggest source, vs. photovoltaics and wind turbines and hydropower) is in cooling the recirculating water. I have an essay on that, in which I also debunk the idea that 40% of our water supply is consumed in power plants.  There are two types of cooling using water – towers that vent evaporating water, which are true water consumers, and once-through flow of water with rejection of warmed water to streams and other bodies of water.  The warmed water evaporates more than in its original, cooler state, but only to the extent of about 8% of the passed-through water or 3% or so of total water use.  We should publish more accurate accounting about power generation.

p. 116, on planting more trees to take up (sequester) carbon from the air and reduce climate change from the business-as-usual scenario (which is horrifying!). The author of this text points out some caveats, about losing competing plants and inviting more diseases and pests in big monocultures. A bigger issue, for me, is water use.  Plants transpire (lose) several hundred molecules of water for each molecule of CO2 taken up…and that’s inflated by the need to maintain tissues and regrow some tissues.  One must also consider that most plant biomass decomposes back to CO2 and other products unless it gets buried well or charred – that’s a lot of work.  Another caveat is that standing biomass, not buried, that we might grow adds up to only about 2 years of CO2 emissions, ever – I’m grateful to Rob Jackson, now at Stanford, for the quantification.  The author(s) of this page rightly point out that more trees is only one part of the solution to climate change, one “wedge.”

p. 117, showing an electric car with a photovoltaic panel on the roof. This is misleading about how much PV area we need, for cars or any other power usage. Covering, say, half the top area of a car with modern panels, about 6 square meters, would provide around 1.2 kW at peak or around 8 kWh over a clear day, maybe 1600 kWh over a year with average weather.  A typical small car used for 15,000 miles of driving a year.  At the normal mix of speeds, it might run at 20 hp or 15 kW for 400 hours to cover those 15,000 miles.  That means it uses 6000 kWh.  Panels on cars don’t make it.

p. 128, bottom, about most oil having come from (decomposed and heat-processed) vegetation. Let’s say that most of it came from plankton in water bodies, especially oceans. Modern taxonomy has these organisms very distinct from vegetation, taken as meaning green higher plants.

p. 129, Elon Musk’s quote about digital intelligence taking over. Musk is a smart person, but his scenario doesn’t ring true to me. Sure, AI and robotics are increasingly used to replace humans for economic reasons and with great economic consequences for humans.  However, live organisms make themselves, remake themselves constantly (we turn over all the elements in our body over our lifetime, some of them frequently).  Robots would need supplies of metals, the refining of semiconductor elements (silicon, e.g.), the ability to put together economic systems, and much more.  I’m worried about corporate and governmental use of AI and robotics, not autonomous self-reproducing robots.

p. 130, on cyanobacteria producing free oxygen as an atmospheric poison to other existing life forms 2.2 billion years ago, all anaerobes poorly tolerating oxygen of finding it lethal. The biggest part of the threat that cyanobacteria and their O2 production posed to other life forms was creating Snowball Earth. The oxygen oxidized methane that massively dominated over CO2 in the early atmosphere.  This severely reduced the methane greenhouse effect, which is more potent that the greenhouse effect from an equivalent amount of CO2.  At that time in Earth’s history, the Sun’s output was as low as 70% of current levels; only a methane greenhouse effect kept the Earth warm enough to be largely ice-free.  When the methane got oxidized, the Earth’s surface froze over almost entirely, as shown by many pieces of evidence, including drop stones from glaciers being found all over the Earth at that time, now buried for “reading” in sedimentary rocks of that age.

Did free oxygen accumulate in high-enough concentration to be itself a threat to other, anaerobic life forms?  I wasn’t there, but here’s a hypothesis, that O2 reached moderate concentrations only locally.  There were many geographic niches by depth and lat/long for anaerobes.  In general, O2 levels remained very, very low, because there were many other “users” of oxygen that scarfed it up even at those low levels.  I’d point to the ferrous iron that was in the then-green oceans and that precipitated out in highly insoluble ferric iron compounds as it got oxidized.  It formed the red bands that ae so thick and so striking – visit the Grand Canyon to see them.  Methane itself was another “sink” for O2, though one has to guess how it reacted at low levels of O2; catalytic sites might have helped.

p. 131, on solar flares threatening operations in our modern civilization. I’d elaborate on this. Taking out the electric grid in the US for more than several months would cause massive death.  Most people live in cities far from farms; little food would be reaching them with transportation stymied by a low level of fuel-pumping capacity for vehicles, plus a near absence of financial transaction capacity, and more.  The same factors affect the ability to grow food on farms, where much fossil fuel and electricity is used.  Severe fuel shortages also would prevent most people from migrating to food sources.  And so on.  Keep that electric grid up!  Don’t fail to protect it from solar flares, cyberwar, and plain old wearing out.

p. 139, on vegans doing better nutritionally in nonindustrialized countries. The author attributes better nutrition there to contamination with insect carcasses as protein sources. That’s a minor factor; while protein is in short supply in many countries, it’s pure calories that are in even shorter supply.  I point, instead, to microbial contamination as the benefit.  Only microbes make vitamin B12.  Really clean vegetable matter lacks vitamin B12, which we need but plants don’t.  Mix in some dirt!

p. 149, on visual thinking done by people, notably Dr. Temple Grandin, who is autistic. I am impressed by her abilities. On the other hand, I am sad at having seen so many university students who have severely limited abilities to think in words while claiming to be visual learners.  Tell me how you can reason by putting images together.

pp. 166 ff., Section Four, about science fiction, including so much on zombies and aliens. It may attract some readers, but I find it rather pandering to pop culture and attendant anti-intellectualism. Sigh.

pp. 198, 199, which I laud, on unrealism in many movies about space. Yes, let’s keep up the critical thinking!

 

The End

 

 

New Mexico Climate Conference, 28 Oct. 2017

30 November 2017.  My presentation at the New Mexico statewide climate conference on 28 October is up on YouTube.  I spoke about the biological effects of climate change, which have concerned me for decades.  The conference was organized by the Citizens Climate Lobby, as the first of its kind for the CCL.  It linked presenters and audiences by Zoom videoconferencing in 4 cities – Las Cruces, Albuquerque, Santa Fe, and Taos.  John Nelson and I organized the presentation down here.

Kelp won’t save us, alas

19 October 2017.  National Geographic misses the math.  In the November 2017 issue you’ll find a two-page spread entitled Kelp is on the Way.  The premise is that, if we begin farming kelp in a big way for food, it “could remove billions of metric tons of carbon dioxide from the atmosphere.”  Here are the real limitations:

  • If we eat kelp and metabolize it, all the carbon in the kelp goes back into the atmosphere as CO2 in our breath.  The only way to keep the carbon sequestered is to prevent it being metabolized.  One scheme touted at least a decade ago is to harvest trees and bury them.  That could hold the carbon back for centuries to millenia, giving us time to fix our energy economy.  Kelp will not.  Rather in reverse, what goes down (C in our food) must come up (in our breath).
  • Let’s not forget the fossil fuel usage in harvesting and transporting the kelp or kelp products.   Processing and transport is a big part of all crop production and use.
  • The global area suitable for kelp farming is very small, compared even to land-based crop area.  It’s the continental shelves, and not too far out.  Of course, if you want to put kelp on platforms in the open ocean… good luck.
  • Will kelp grow without (added) nitrogen and phosphorus fertilizers, or even take up the N and P that we add in sewage or in cropland runoff?  The marine ecologist cited in the entry is indirectly referencing some big inputs, such as the Mississippi River basin.   Runoff of excess fertilizer, mostly, from over 1 million km2 of crops, puts enough N and P into the river delta to cause a massive algal bloom each year, over tens of thousands of km2.  The dieback of the algae and subsequent decomposition  deoxygenates the water with disastrous consequences for marine life.  OK, but the big N and P inputs are at major river deltas, not the whole set of continental margins.  Sure, many margins have upwelling of nutrient-rich waters, but the coverage is not good.

Kelp might be healthful as a food.  It’s not a CO2 sink, by any means.

(Photo: National Geographic)